We purchased 6 Replacement windows from Omni in the early 90s. We had a bow window installed in approximately 1994. The problem we're having is that the seat of the window that extends from the house has started to dry rot and is causing air to escape the house. We live in Indianapolis, Indiana and Omni no longer has an office here. Is there any way to contact the manufacturer to get a read on a solution. The seat is made of what appears to be 1/2 or 3/4 inch plywood. Is this possible to repair or will the window need to be replaced?

Best if you get local help on that. You have no warranty on that.
It could be a mfg problem or an install problem.
You have at least two concerns:
structure
appearance
The outside needs to be sealed, windows to seat board, seat board front face and bottom.
Once that is done then it probalby can have the seat board laminate with an oak veneer plywood.